A well tray comprises an array of cylindrical wells for storing and growing samples of genetic material. By way of example, a product marketed by Corning Glass Works, Corning, N.Y., under the trademark "CELL WELLS" comprises a 6.times.4 array of 16-mm diameter wells, each 18 mm deep. The well tray is molded of plastic such as clear polystyrene and has approximate outside dimensions of 85 mm.times.127 mm.times.22 mm.
Certain procedures such as electrofusion and electroporation require subjecting the samples to an electric field. Treating a sample entails withdrawing the sample from a flask or cuvette, placing the sample in a cell having suitably configured electrodes (called an electrode cell), treating the sample according to the desired procedure, removing the sample from the electrode cell, placing the sample in a well, and flushing the electrode cell to clean it for subsequent samples. Depending on the nature of the electrode cell, the cleaning step may represent a significant bottleneck in the process, and may present a risk of contamination.